We want to calculate the daily aggregate collection amount using shovel from the aggregate collection center. Shovel's aggregate collection is related to the density of aggregates. When classifying the density of aggregates into 4 grades(D1,D2,D3,D4), the density of target aggregates is expected to be as follows.

P(D1)=0.2, P(D2)=0.4, P(D3)=0.3, P(D4)=0.1

->The daily amount of aggregate collected by Shobel according to each closeness has the following probability.

Daily collection	D1	D2	D3	D4
X1=800	0.1	0.2	0.3	0.4
X2=900	0.2	0.3	0.3	0.3
X3=1000	0.4	0.3	0.3	0.2
X4=1100	0.3	0.2	0.1	0.1

Question.

What is the expected value of daily aggregate collection?