How could I solve c) and d) without the use of derivatives for the following question?

Question

It is estimated that, t years from now, the amount of waste accumulated, Q, in tonnes, will be Q(t)= 10^4(t^2+15t+70) tonnes, t is greater than or equal to 0, t is also less than or equal to 10.

b) What will the average rate of change of this quauntity over the next three years?

c) What is the present rate of change of this quantity?

d) When will the rate of change reach 3.0 * 10^5 tonnes per year?

Answer 1

This little essay should help.

http://jwilson.coe.uga.edu/EMAT6680Fa2012/Faircloth/Essay4alf/TangentLine.html