1. (10%) Given below is a bivariate distribution for the random variables a and b. Find the correlation coefficient of a and b.

| f(a, b) | a | b |
| --- | --- | --- |
| 0.2 | 50 | 80 |
| 0.3 | 40 | 60 |
| 0.5 | 30 | 50 |

(Note: You are being asked to calculate to two decimal places)