We know that:
Cost (Cranberry Juice): 6.3 per quart
Cost (Apple Juice): 3.6 per quart
Quantity (Apple Juice): 4 quarts
Quantity (Cranberry Juice): q quarts
Further we know that Terrence wants the cost of the juice to be 4.5 per quart
Hence Total Cost = Cost per quart × Total Number of quarts = (Cost per quart for Apple Juice × Total Number of Apple Juice Quarts) + (Cost per quart for Cranberry Juice × Total Number of Cranberry Juice Quarts)
⇒ Total Cost = 4.5 × (q+4) = 6.3 × q + 3.6 × 4
⇒ 4.5(q+4) = 6.3q + 14.4, which matches with option D
Hence, the correct option is D