When the afferent arteriole dilates and the efferent arteriole constricts, the net filtration pressure (NFP) in the glomerulus will increase.
This occurs because the dilation of the afferent arteriole allows more blood to flow into the glomerulus, increasing the glomerular blood pressure. At the same time, the constriction of the efferent arteriole reduces the outflow of blood from the glomerulus, further increasing the pressure within this capillary network.
The overall effect is a higher net filtration pressure, which enhances the filtration of blood into the Bowman’s capsule and subsequently increases urine production. Therefore, the answer is b) increase.