SHARYGIN 2006 Problem 4

a) Given two squares $ABCD$ and $DEFG$ , with point $E$ lying on the segment $CD$ , and points $F,G$ outside the square $ABCD$ . Find the angle between lines $AE$ and $BF$ . b) Two regular pentagons $OKLMN$ and $OPRST$ are given, and the point $P$ lies on the segment $ON$ , and the points $R, S, T$ are outside the pentagon $OKLMN$ . Find the angle between straight lines $KP$ and $MS$ .