To find the total cost \( c \) that Vicky paid for the oranges, we can use the equation:
\[ c = \text{(cost per pound)} \times \text{(number of pounds)} \]
In this case, the cost per pound is $3.90 and the number of pounds is 312. Therefore, the equation can be represented as:
\[ c = 3.90 \times 312 \]
Calculating \( c \):
\[ c = 3.90 \times 312 = 1219.80 \]
Vicky paid $1219.80 in total for the oranges.
However, none of the given responses directly represent the correct relationship between the variables given the context provided. The correct equation should be:
\[ c = 3.90 \times 312 \]
If you need to choose the closest option, none of them accurately represent the total cost \( c \) based on the information given. Please check the options again, or perhaps there was a misunderstanding in the terms of the problem.