# Constants for default values and messages

WELCOME$\_$TEXT $=$ "Welcome to the Mortgage Calculator!"

MAIN$\_$PROMPT $="$Do you wish to process a new mortgage? $($Y$/$N$)$: $"$

LOCATION$\_$NOT$\_$KNOWN$\_$TEXT $=$ "Location not recognized. Using national averages."

# Property tax rates and real estate prices per square foot by location

location$\_$data $=\{$

"Seattle": $\{"$tax$\_$rate": $0\mathrm{.}01,$ "price$\_$per$\_$sqft$"$: $500\},$

"San Francisco": $\{"$tax$\_$rate": $0\mathrm{.}012,$ "price$\_$per$\_$sqft$"$: $800\},$

"Austin": $\{"$tax$\_$rate": $0\mathrm{.}008,$ "price$\_$per$\_$sqft$"$: $300\},$

"East Lansing": $\{"$tax$\_$rate": $0\mathrm{.}011,$ "price$\_$per$\_$sqft$"$: $250\}$

$\}$

# National averages

AVERAGE$\_$NATIONAL$\_$PROPERTY$\_$TAX$\_$RATE $=0\mathrm{.}01$

AVERAGE$\_$NATIONAL$\_$PRICE$\_$PER$\_$SQ$\_$FOOT $=200$

APR$\_2023=3\mathrm{.}5$ # Default APR value if not provided

def get$\_$user$\_$input$($prompt$,$ data$\_$type$=$float, default$=\text{'}$NA$\text{'})$:

$"""$Get user input and convert to specified data type, or return default."""

user$\_$input $=$ input$($prompt$)$

if user$\_$input.upper$()==\text{'}$NA$\text{'}$:

return default

return data$\_$type$($user$\_$input$)$

def main$()$:

print$($WELCOME$\_$TEXT$)$

while True:

if input$($MAIN$\_$PROMPT$).$upper$()!=\text{'}$Y$\text{'}$:

print$("$Thank you for using the Mortgage Calculator."$)$

break

# User inputs

location $=$ input$("$Enter the desired location of the house: $")$

square$\_$footage $=$ get$\_$user$\_$input$("$Enter the desired square footage: $",$ default$=\text{'}$NA$\text{'})$

max$\_$monthly$\_$payment $=$ get$\_$user$\_$input$("$Enter the desired maximum monthly payment: $",$ default$=\text{'}$NA$\text{'})$

down$\_$payment $=$ get$\_$user$\_$input$("$Enter the expected down payment: $",$ default$=0\mathrm{.}0)$

apr $=$ get$\_$user$\_$input$("$Enter the current APR: $",$ default$=$APR$\_2023)/100$ # Convert percentage to fraction

# Handle location

if location in location$\_$data:

tax$\_$rate $=$ location$\_$data$[$location$][\text{'}$tax$\_$rate'$]$

price$\_$per$\_$sqft $=$ location$\_$data$[$location$][\text{'}$price$\_$per$\_$sqft$\text{'}]$

else:

print$($LOCATION$\_$NOT$\_$KNOWN$\_$TEXT$)$

tax$\_$rate $=$ AVERAGE$\_$NATIONAL$\_$PROPERTY$\_$TAX$\_$RATE

price$\_$per$\_$sqft $=$ AVERAGE$\_$NATIONAL$\_$PRICE$\_$PER$\_$SQ$\_$FOOT

# Calculations and output logic based on provided inputs

# This is where you'd implement the logic for the different cases

# For example, for case $1($square footage only$)$:

if square$\_$footage $!=\text{'}$NA$\text{'}$ and max$\_$monthly$\_$payment $==\text{'}$NA$\text{'}$:

# Implement calculation logic here

pass

# Similarly, handle other cases...

if $\_\_$name$\_\_=="\_\_$main$\_\_"$:

main$()$