-   function expansion(IMarket market, uint amount) public {
+   function expansion(IMarket market, uint amount) public noReentrant {
        ...
    }

-   function contraction(IMarket market, uint amount) public {
+   function contraction(IMarket market, uint amount) public noReentrant {
        ...
    }
    function getEscrow(address user) internal returns (IEscrow) {
        if(escrows[user] != IEscrow(address(0))) return escrows[user];
        IEscrow escrow = createEscrow(user);
        escrow.initialize(collateral, user);
        escrows[user] = escrow;
        return escrow;
    }
