Sum units in a table.

Goal

Print 25 units and Nairobi as busiest.

local rows = {
  { city = "Nairobi", units = 12, shillings = 480 },
  { city = "Mombasa", units = 8, shillings = 320 },
  { city = "Kisumu", units = 5, shillings = 200 },
}
local units, shillings, busiest = 0, 0, rows[1]
for _, r in ipairs(rows) do
  units = units + r.units
  shillings = shillings + r.shillings
  if r.units > busiest.units then busiest = r end
end
print("units", units)
print("shillings", shillings)
print("busiest", busiest.city)