Table:
text: Crawley
Neighbourhoods and areas
Neighbourhoods and areas
Number_on_map Name_ Colour Construction_commenced Population
1 Langley Green Grey 1952 7286
2 Northgate Dark green 1951 4407
3 Pound Hill Orange 1953 14716
4 Maidenbower Blue 1987 8070
5 Furnace Green Light green 1960 5734
6 Tilgate Red 1955 6198
7 Broadfield Sky blue 1969 12666
8 Bewbush Light brown 1975 9081
9 Ifield Purple 1953 8414
10 West Green Dark blue 1949 4404
11 Gossops Green Maroon 1956 5014
12 Southgate Brown 1955 8106
13 Three Bridges Yellow 1952 5648

Question: What is the average number for Northgate, which began construction in Crawley before 1951?

Question: What is the lowest population for the blue neighborhood built in Crawley before 1987?