To calculate the trend projection for period 10, substitute t = 10 into the linear trend equation:

$T = 17.5 + 0.65 \times 10$

First, calculate $0.65 \times 10 = 6.5$

Then add: $17.5 + 6.5 = 24$

Therefore, the trend projection for period 10 is 24.

Verification:

• Option A (28.15) would result from using t=16.5 instead of t=10
• Option B (181.5) would result from using t=252.3 instead of t=10
• Option C (82.5) would result from using t=100 instead of t=10
• Option D (24) is the correct calculation