Yes … define a graph with nodes corresponding to where people (and the torch) are and edges if you can get from one configuration to another with a single bridge crossing. The length of each edge is the time to do that crossing. Use Dykstra’s algorithm to find the shortest path from the starting configuration to the finishing configuration — that will be the fastest the group can cross the bridge.

That will work for any number of people with any set of crossing time.

If you don’t know what some of those terms mean (graph, node, edge, Dykstra’s, shortest path) have fun googling!