The dartboard consists of concentric circles of radius r, 2r, ..., 10r (r> 0 is constant).

The outermost circle of them gives one point, the next two points,

etc. The circle in the middle gives 10 points. Suppose that when thrown into the board

the probability of each sub-area is proportional to its area.

1. Specify with one board hitting dart

the expected value and variance of the score obtained with said dart.