What are the domain and range of the function a) {x| x is a real number}; {y|y> 0}b) {x| x> 4}; {y|y> 0}c) {x| x is a real number}; {y|y> 4}d) {x|x> 4}; {y|y> 4}

We have the following function:
 f (x) = 4 * ((81) ^ (1/3)) ^ x
 We observed that:
 (81) ^ (1/3) = 4.326748711> 1
 Therefore the function grows as it increases and decreases as x decreases.
 We have then:
 Domain: all reals.
 Range: all reals greater than zero.
 
 A) {x | x is a real number}; {y | y> 0}

Ithink the answer is b