Added solutions to remaining problem files.

pr10.cql

 .in
-B:1
+S:3,
+T:3
 
 .out
-B;
\ No newline at end of file
+S x T;
+filter (\(r) -> r[1]==r[2] and r[5]==r[6]);
+map (\(r) -> r[3,4]);

pr8.cql

+.in
+P:4,
+Q:4
+
+.out
+P x Q;
+filter (\(r) -> r[4]==r[8]);
+let f = \(p,q) -> if (isEmpty(q)) then p else q;
+map (\(r) -> [f(r[1],r[5]), f(r[2], r[6]), f(r[3], r[7]), f(r[4], r[8])]);

pr9.cql

+.in
+R:2
+
+.out
+R x R x R;
+
+filter ( \(r) -> 
+                    r[2] == r[3]
+                    and
+                    r[4] == r[5]
+                 
+        );
+map (\(r) -> r[1,6]);