A TV manufacturer produced 600 units in the third year and 700 units in the seventh year. What was the production in the first year?

Assume the production follows an arithmetic progression, where the number of units increases linearly each year. Let the first year’s production be a, and the common difference be d. Step 1: The third year’s production is a + 2d = 600 (1). The seventh year’s production is a + 6d = 700 (2). Step 2: Subtract (1) from (2): (a + 6d) - (a + 2d) = 700 - 600, so 4d = 100, d = 25. Step 3: Substitute d = 25 in (1): a + 2(25) = 600, a + 50 = 600, a = 550. Verify: Seventh year = 550 + 6(25) = 550 + 150 = 700, which holds. Options A, C, and D are incorrect. Thus, the correct answer is B.