The current density in a region is js = xyˆaz [A/m²], where x and y are specified in meters. Find the current i flowing towards increasing values of z through the surface −1 < x < 1, −1 < y < 1, z = 0.

a) ∫∫ (xy)dxdy
b) ∫∫ (x² + y²)dxdy
c) ∫∫ (xy + z)dxdy
d) ∫∫ (x + y)dxdy