Maria saves $3.87∗10^5 every five years If she continues to save at this constant rate, how much money can she save in 27 years? Express your answer in both standard and scientific notation

The volume of a spherical hot air balloon v(r) = 4 3 ? r3 changes as its radius changes. the radius is a function of time given by r(t) = 3t. find the instantaneous rate of change of the volume with respect to t at t = 2.