问题：
[填空题]
The below figure shows a flow network on which an s−t flow has been computed. The capacity of each edge appears as a label next to the edge, and the numbers in boxes give the amount of flow sent on each edge. (Edges without boxed numbers have no flow being sent on them.)
a) The value of this flow is ____.
b) The value of the maximum s−t flow in this graph is ____.
