Bipartite Graphs and Matchings · Easy problem

Two staff members, Alex and Blair, can each be assigned to help with tasks labeled $1,2,3,4$. Alex can help with any of the four tasks; Blair can help with tasks $1$, $2$, or $3$, but not task $4$. What is the maximum number of tasks that can be staffed at the same time, with each staff member assigned to at most one task?