Add minutes spent and minor syntax

A1/infix-ae.rkt

@@ -1,5 +1,7 @@
 #lang plait
 
+(define minutes-spent 50)
+
 #| BNF for the AE language:
    ae: NUMBER
        | { ae + ae }
@@ -40,7 +42,7 @@
     [(Add l r) (+ (eval l) (eval r))]
     [(Sub l r) (- (eval l) (eval r))]
     [(Mul l r) (* (eval l) (eval r))]
-    [(Div l r) (if(equal? 0 (eval r))
+    [(Div l r) (if (equal? 0 (eval r))
                   (cond
                     [(< 0 (eval l)) +inf.0]
                     [(> 0 (eval l)) -inf.0]