Ct from deplotted data for seven thresholds
Fth\X0 188000   18800    1880     188    18.8
 500	13.90	17.50	20.98	24.50	27.96
1000	15.03	18.60	22.07	25.82	29.07
2000	16.17	19.77	23.17	26.91	30.18
3000	17.09	20.63	24.04	27.69	30.96
5000	18.28	21.90	25.26	28.96	32.26
7000	19.47	23.09	26.42	30.07	33.50
9000	21.25	24.88	27.93	31.67	35.64