added source for parking lot and fixed formula

linear_program.py

@@ -60,10 +60,11 @@ def calculate(floors=1, xLength=1, yLength=1):
     # cost is 8.99 each from https://sequoiatrees.com/products/rainbow-eucalyptus-mini-grow-kit
     cost += 100*8.99*eucalyptusTreeAcres
     # asphalt parking lot cost of 2$ per square foot from https://www.miconcrete.org/concrete-parking-lot-and-your-business
+    # size of a parking space is 153 square feet from https://www.dimensions.com/element/parking-spaces
     # the cost of each space is 15*10.7639*2 dollars
-    # parking space ratio is determined to be 1 space:250 square feet
-    # use 162/15 as a ratio to convert to square feet, divide by 250 to get parking spaces, and multiply by 324 to get cost
-    cost += ((xLength*yLength*floors)*10.7639/250)*(15*10.7639*2)
+    # parking space ratio is determined to be 1 space:250 square feet from https://www.commercialrealestate.loans/commercial-real-estate-glossary/parking-ratio/#:~:text=May%20Be%20Increasing-,Research%20suggests%20that%20office%20building%20tenants%20are%20asking%20for%20more%20parking,parking%20ratio%20is%20currently%20around%204%20spots%20per%201%2C000%20square%20feet,-%2C%20many%20tenants%20have
+    # use 10.7639 to convert to square feet, divide by 250 to get parking spaces, and multiply by 153*2 to get cost.
+    cost += ((xLength*yLength*floors)*10.7639/250)*(153*2)
 
     # constraints
     constraints = []