please explain RRR and solve a and b

S. A machine (with a 5-year life span) is expected to provide the following cash flows: Year 1 Year 2 Year 3 Year 4 Year 5 + $1 mill $1.5 mill $2 mill $2.5 mill $3 mill What's the maximum you should pay for this machine (your RRR is 12%)? b) Given your minimum required rate of return is 12%, would you buy this machine for $7.5 million