Can someone help me with this radiochemistry question please?

[shenzys]

So the question is:

Calculate the radioactive concentration (MBq/ml) of a sodium pertechnetate [99mTC] solution with a concentration of 2.0 * 10^-6 g/L.

Mr (sodium pertechnetate) = 186
half life of [99mTc) = 6.02 hours
Avagadro's constant = 6.02 * 10^23

Okay, so the first step would be to work out the decay constant (lamda) from the half life which I can do but, after that I kind of get stuck. Do I need to calculate the activity (A) by using the formula A= lamda N?
How do I work out N if I don't have the mass to work out the moles of the compound? And then how does that enable me to work out the concentration using c=n/v without a volume

Also, am I going about the question the correct way?

[Pharmanaut]

So the question is:

Calculate the radioactive concentration (MBq/ml) of a sodium pertechnetate [99mTC] solution with a concentration of 2.0 * 10^-6 g/L.

Mr (sodium pertechnetate) = 186
half life of [99mTc) = 6.02 hours
Avagadro's constant = 6.02 * 10^23

Okay, so the first step would be to work out the decay constant (lamda) from the half life which I can do but, after that I kind of get stuck. Do I need to calculate the activity (A) by using the formula A= lamda N?
How do I work out N if I don't have the mass to work out the moles of the compound? And then how does that enable me to work out the concentration using c=n/v without a volume

Also, am I going about the question the correct way?

Its years since I last worked out one of these.
Have a think about the concentration.
"solution with a concentration of 2.0 * 10^-6 g/L."
Gives you the mass per litre, just assume you are playing with a litre of the stuff.

[Nik]

So the question is:

Calculate the radioactive concentration (MBq/ml) of a sodium pertechnetate [99mTC] solution with a concentration of 2.0 * 10^-6 g/L.

Mr (sodium pertechnetate) = 186
half life of [99mTc) = 6.02 hours
Avagadro's constant = 6.02 * 10^23

Okay, so the first step would be to work out the decay constant (lamda) from the half life which I can do but, after that I kind of get stuck. Do I need to calculate the activity (A) by using the formula A= lamda N?
How do I work out N if I don't have the mass to work out the moles of the compound? And then how does that enable me to work out the concentration using c=n/v without a volume

Also, am I going about the question the correct way?

Radiopharmacy is interesting but I'm useless at physics so I don't know the correct method. However I can give you a tip - you are given mass if I'm not mistaken, as you quoted conc = 2x10^-6g/L. Easy peasy stuff to start: use equation no of moles = mass/Mr to get N.