Can someone explain how to start this problem?

To test the efficacy of a new cholesterol-lowering medication, 10 people are selected at random. Each has their LDL levels measured (shown below as Before), then take the medicine for 10 weeks, and then has their LDL levels measured again (After). Subject Before After 199 208 170 184 131 108 137 128 155 139 193 154 174 172 142 112 164 147 10 119 87 Give a 98% confidence interval for the difference between LDL levels before and after taking the medication. Confidence Interval =