这是我目前写的，但似乎无法弄清楚我哪里出错了。我的函数是所以我知道答案应该是什么，只需要一点指导就可以到达那里。谁能告诉我哪里出错了？$f(x)=\exp(x)$

REAL :: a, b, f, h, SUM, integral
INTEGER :: i, n

WRITE(*,*) "WHAT IS LOWER LIMIT?"
READ(*,*) a

WRITE(*,*) "WHAT IS UPPER LIMIT?"
READ(*,*) b

WRITE(*,*) "WHAT IS THE NUMBER OF SUB-INTERVALS?"
READ(*,*) n

h = (b - a) / n

SUM = 0.0
SUM = (7*f(a+b) + 32*(f(a+h) + f(b-h)) + 12*f(a+2*h))

integral = 2*SUM *h / 45

WRITE (*,*) "THE VALUE IS", integral