Find the differential of the function. z = x ln(y⁴ + 8) dz = dx + dy
a) dz = dx + 4y³ * dy
b) dz = dx + 4y³/(y⁴ + 8) * dy
c) dz = dx + 4y³/(y⁴ + 1) * dy
d) dz = dx + 4y²/(y⁴ + 8) * dy