The question you are looking at is good .... refer to FIG 4.2 ... Short Distance Cruise Altitude - enter at 150nm, up to the 'ISA +10C and below' curve, across to the REF LINE (make a pencil mark), follow the adjustment curve to the BRW condition 57000kg, now read the scale. I get a fraction over 25000ft.

Now FIG 4.5.3.2 .... 25000ft .... CAP 697 S4 P41 ... TAS 445 kts .... apply TEMP correction NOTE 2 (B) .... ISA-10, -10kts, so TAS 435kts.