An old man's son has just died. How to choose a cemetery for the elderly?

Emperor Taizong, the eldest son is on the top and the eldest son is on the lower right, put the grave of the old man 3 meters below his father, 3 meters to the right of the grave of the old man and 3 meters below the grave of the second son, but the grave of the second son and the grave of the eldest son are not on the same level, that is, the grave of the second son goes down 33.3 centimeters. The distance between the eldest son grave and the second son grave is 7 meters.