If a stock went up from $45.00 to $48.25 last week, and the S&P 500 (representing the market) went down from 2,550 to 2,230 last week, what would be the implied beta for the stock (if this is the only information you have)?*

a. -0.4697 b. -0.5033 c. -0.4100 d. -0.5755 e. -0.5367

*correct answer given is D.

If this could be answered in the most simple step-by-step that would be appreciated.