5. Cesium-137 is a radioactive isotope. The following formula represents the remaining amount of a 300 gram sample of cesium-137 in a storage tank after t years:

N(t)=300e−0.02297t

A) Determine the remaining amount of cesium-137 in the storage tank after 75 years. (Round to the nearest whole number.)

B) Find the number of years it takes for the original sample to decay to 7 mg. (Round to the nearest whole number.)

what's the trouble? You have the formula; just plug in your values.