But if you shrink that diameter to what we're attempting, which is 12 feet, which is plenty to get an electric skate through, you drop the diameter by a factor of two and the cross-sectional area by a factor of four, and the tunneling cost scales with the cross-sectional area.
Međutim, ako suzite promjer kako mi namjeravamo, a to je 3.6 metara, što je dovoljno za prolazak električnog nosača, tunel ste prepolovili a prostor poprečnog presjeka četverostruko umanjili, a cijena kopanja tunela ovisi o veličini poprečnog presjeka.