To find the corresponding cost \( c \) when \( m = 4.5 \) miles, you can substitute \( m \) into the linear function:
\[ c = 0.75m + 4 \]
Substituting \( m = 4.5 \):
\[ c = 0.75(4.5) + 4 \]
Now calculate \( 0.75 \times 4.5 \):
\[ 0.75 \times 4.5 = 3.375 \]
Now add this to the base fare of $4:
\[ c = 3.375 + 4 = 7.375 \]
So, the corresponding cost \( c \) for traveling 4.5 miles is approximately:
\[ c \approx 7.38 \text{ (rounded to the nearest hundredth)} \]
Thus, the final answer is \( \mathbf{7.38} \).