Please explain by steps

The owners of a chain of fast- food restaurants spend $30 million installing donut makers in all their restaurants. This is expected to increase cash flows by $8 million per year for the next five years. If the discount rate is 6.2%, were the owners correct in making the decision to install donut makers?

A) Yes, as it has a net present value (NPV) of $2.11 million.

B) No, as it has a net present value (NPV) of -$0.70 million.

C) No, as it has a net present value (NPV) of -$0.35 million.

D) Yes, as it has a net present value (NPV) of $3.52 million.

The correst answer is D, but how?