the state wants to build a new stretch of highway to link an existing bridge with a turnpike interchange, located 8 mile

[answerhappygod]

the state wants to build a new stretch of highway to link an existing bridge with a turnpike interchange, located 8 miles to the south of the bridge. there is a 5 mile wide stretch of marshland adjacent to the bridge that must be crossed. given that the highway costs 10 millions dollars per mile to build over the marsh and only 7 millions dollars per mile to build over dry land, how far to the east of the bridge should the highway be when it crosses out of the marsh?