region field: ['611/400', '776887/500000', '9/25', '471/1000']
box hull: u [611/400 , 776887/500000] = [1.5275, 1.553774], t [9/25, 471/1000] = [0.360000, 0.471000]
a(t) range: [0.637394, 0.770968]; needs a(T1) <= 16/25: True, a(T2) >= 77/100: True
tiling of hull: OK
boxes 641, failures 0, certified sub-boxes 75008, max depth 5, 2.2s
