Trivial to remark: if $x$ works, so do $180-x$ with the other money. * Claim: each $2$ people can give each number from $45$ to $75$ Proof: For $x \in \{0,1,2...15\}$, person $A$ can pay $x$ with change to $B$ and so $A$ leaves with $60-x$, $B$ with $60+x$. Next, as $A$ can pay $B$ $15$ Reo, $A$ can give a number between $15$ and $45$ Reo, or else $B$ can give A a number of Reo's between $30$ and $45$ back. So there is a person who can pay $t$ with $15 \le t \le 30$. (by $*$ ) Together with the other two people they can pay each number between $45+t \le 75$ and $75+t \ge 90$.