Ride 5 mile warm up then 10 miles hard/ followed by 2 mile hard run. Get back on bike and ride 10 miles hard again followed by a 2 mile hard run. Easy cool down.
'Hard' effort: RPE=7/8
4 miles off bike - see above- sequence should be 5+10 mile bike/ 2 mile run - 10 mile bike/2 mile run.