It is known that an insurance company will pay a maximum of 3 claims for natural disasters in 1 year. Suppose X is the number of natural disasters with a minimum loss of 10 billion and Y is the total number of natural disasters that occur. The joint density function is also known as follows: f(x,y) = c(x+2y) ; x=0,1,2,3 ; y=0,1,2,3, x<=y = 0 ; otherwise

Where c is a constant. Determine the expectation of the number of natural disasters that occur with losses under 10 billion

The answer is 1,1 please explain why??