Jack and Jill took a trip to Grandma’s house. It took them 8 hr to get to Grandma’s house but on their way back home they took the scenic route, which is 20 mi longer. If their speed going home was 10 mi/hr less than their speed going to Grandma’s house, and if it took them 10 hr to get home, how far did they travel going to Grandma’s and what was their average speed on the trip there?