Prior working overseas, Spouse A agreed to pay his spouse B $($stay$-$at$-$home mom$)$ a montly allowance to support the expenses and their children's monthly subsistence. However, when A is working oversea, the marriage has fallen apart and B wanted a divorce. A told B that he would stop granting monthly allowance. B agrued that there was a contractual agreement between husband and wife. Under contract law $($Australia$),$ can B sue A for the maintainance of monthly allowance?