Evaluate the expression if \( x=5, y=-7 \) and \( a=7 \). \( 3 x-4 y+4 a \) Select the correct choice below and, if necessary, fill in the answer box to complete your choice. A. \( 3 x-4 y+4 a=\square \) (Type an integer or a simplified fraction.) B. The answer is undefined.

We are given the expression \[ 3x - 4y + 4a \] and the values \[ x = 5,\quad y = -7,\quad a = 7. \] **Step 1. Substitute the values into the expression:** \[ 3(5) - 4(-7) + 4(7) \] **Step 2. Multiply the terms:** \[ 15 + 28 + 28 \] **Step 3. Add the results:** \[ 15 + 28 = 43,\quad 43 + 28 = 71 \] Thus, the evaluated expression is \[ 3x - 4y + 4a = 71. \] The correct choice is A. \( 3x - 4y + 4a = 71 \).