Answer:
10℉
Explanation:
9,000 feet - 4000 feet (because the camp is 4000 feet above sea level) = 5000 feet
for every 1000 ft you decrease by 3.6℉ therefore 5(3.6) = 18 degrees
when you get to the top it is -8℉ to find out the temp at base camp you just add 18 ℉ to the final tempreture
-8 +18 = 10℉