To find the extra cost of feeding one additional person, we start with the formula for the cost \( Q \):

\(Q = 1.5 + 0.5n\)

Calculate the cost for \( n \)
 \(Q(n) = 1.5 + 0.5n\)

Calculate the cost for \( n + 1 \)
 \(Q(n + 1) = 1.5 + 0.5(n + 1) = 1.5 + 0.5n + 0.5 = 2 + 0.5n\)

Find the extra cost
 \(\text{Extra cost} = Q(n + 1) - Q(n) = (2 + 0.5n) - (1.5 + 0.5n) = 2 - 1.5 = 0.5\)

The extra cost of feeding one additional person is \( 0.5 \) Naira.

To convert this to kobo (since \( 1 \) Naira = \( 100 \) kobo):
\(0.5 \text{ Naira} = 0.5 \times 100 = 50 \text{ kobo}\)

Thus, the extra cost of feeding one additional person is \( 50 \) kobo.