The cost of underestimating the demand is considered a revenue loss that arises due to cancellation of flight costing $134. Hence, cost of underetimating the demand is [tex]C_u=\$134[/tex].
The cost of overestimating the demand is known as rewards. For example, free round trip ticket worth $263. Hence, the cost of overestimating the demand is [tex]C_o=\$263[/tex].
[tex] \frac{C_u}{C_u+C_o} = \frac{134}{134+263} \\ \\ = \frac{134}{397} =0.3375[/tex]
The z-score that yields a p-value of 0.3375 is -0.4193.
Thus, super discount airlines should overbook the flight by 35 + (-0.4193 x 24) = 35 - 10.0632 = 24.9368 = 25 seats.
Therefore, super discount airlines should overbook the flight by 25 seats.