(a) When the four resistors are wired in series, their total resistance equals the sum of their individual resistances, which is the greatest. 4 + 8 + 12 + 24 = 48 is the total equivalent resistance of the resistors linked in series.

(b) The equivalent resistances of the resistors will be the lowest if they are linked in parallel.

When they are linked in parallel, their corresponding resistance is

As a result, the overall resistance with the lowest value is 2.