Can someone help me with this study guide question I'm having a hard time comprehending it!

A doll sold for $250 in 1980 and was sold again in 1985 for $405. Assume that the growth in the value V of thecollector's item was exponential.

a) Find the value k of the exponential growth rate. Assume Vo=250.

k=__________

b) Find the exponential growth function in terms oft, where t is the number of years since 1980.

V(t)=_______

c) Estimate the value of the doll in 2014.

$_____________

d) What is the doubling time for the value of the doll to the nearest tenth of ayear?

_____________

e) Find the amount of time after which the value of the doll will be $6641.

_________ years