I wrote a a program that calculates the volume of cylinders using named functions and un-named functions, however, i'm having trouble doing the same using the let-form in scheme.

here's my program although it doesn't work

```
(define main6(lambda ()
(let (
(volumec6 (lambda (d h)
(let ( pi (3.14159265))
(* h(* (* (/ d 2)(/ d 2)) 3.14)))
)
)
)
)
)
)
```

it gives me this error

let: bad syntax in: (let ((volumec6 (lambda (d h) (let (pi (3.14159265)) (* h (* (* (/ d 2) (/ d 2)) 3.14)))))))