In this problem we use the change of variables x=5s+t x = 5 s + t , y=s−3t y = s − 3 t to compute the integral ∫r(x+y)da ∫ r ( x + y ) d a , where r r is the parallelogram with vertices (x, y)=(0,0) ( x , y ) = ( 0 , 0 ) , (10,2) ( 10 , 2 ) , (11,−1) ( 11 , − 1 ) , and (1,−3) ( 1 , − 3 ) . first find the magnitude of the jacobian, ∣∣∂(x, y)∂(s, t)∣∣= | ∂ ( x , y ) ∂ ( s , t ) | = . then, with a= a = , b= b = , c= c = , and d= d = , ∫r(x+y)da=∫ba∫dc( ∫ r ( x + y ) d a = ∫ a b ∫ c d ( s+ s + t+ t + )dtds ) d t d s =