An item costs $500 at time t=0 and costs $P in year t. When inflation is r% per year, the price is given by P = 500e^(rt/100)

a) if r is a constant, at what rate is the price rising ( in dollars per year)
1) initially 2) after 2 years
b)now suppose that r is increasing by 0.3 per year when r=4 and t=2. At what rate is the price
increasing at that time?

I can do part a) of this question but cant figure out the solution to part b).

Question

An item costs $500 at time t=0 and costs $P in year t. When inflation is r% per year, the price is given by P = 500e^(rt/100) 

a) if r is a constant, at what rate is the price rising ( in dollars per year)
1) initially 2) after 2 years
b)now suppose that r is increasing by 0.3 per year when r=4 and t=2. At what rate is the price 
increasing at that time?

I can do part a) of this question but cant figure out the solution to part b).