Filling in a two-way ANOVA table from its own consistency constraints

For a given data, the two-way ANOVA table has Source/df/Ss: Treat/5/(unknown, call it $b$); Block/3/4.5; Error/$a$/2.0; Total/23/12.5, with $F$-ratio for Treat denoted $c$. The values of $a,b$ and $c$ are: