If two prime numbers a, B, C and D are different and satisfy the equation a + B = C + D, what is the maximum possible value of a + B?

If two prime numbers a, B, C and D are different and satisfy the equation a + B = C + D, what is the maximum possible value of a + B?

The largest two prime numbers are: 97, 91, 89, 83, just meeting 97 + 83 = 91 + 89, so the maximum value is 180