E fourth term of a geometric sequence is 7, the fifth term is 28/3 , and the kth term is 7168/243 . The solution to which of the following equations gives the value of k ?

a. 4( 3/4 )ˣ⁻⁷ = 7168/243
b. 7( 3/4 )ˣ⁻⁴ = 7168/243
c. 4( 4/3 )ˣ⁻⁷ )= 7168/243
d. 7( 4/3 )ˣ⁻⁴ = 7168/243