Evaluate of function h(3a)=x^4+2a^2+4

If you would like to evaluate function h(x) = x^4 + 2 * a^2 + 4 when x = 3a, you can do this using the following steps:

x = 3a
h(x) = x^4 + 2 * a^2 + 4
h(3a) = (3a)^4 + 2 * a^2 + 4 = 3^4 * a^4 + 2 * a^2 + 4 = 81 * a^4 + 2 * a^2 + 4

The correct result would be h(3a) = 81 * a^4 + 2 * a^2 + 4.

Letter b hope it