In regards to LETTER E, the food store and medical storage. Floors 1 and 2 are lost and have a number of infected. The stairway is mildly blocked, but the hallway going towards the stairs to the floors below are PACKED full of stuff in a fairly secure barricade, AND the actual doors are locked. 

To get to the floors below, they will have to removes those barricades.

Last, there are stairs going up to the roof, where there is a helicopter with VERY little fuel. Enough to take off, get about 1/10th a mile away and land, or crash. 

There also may or may not be 10 to 20 infected up there....

Az