You will need 6 buttons.

Finished measurements:
Cardigan
Bust circumference: 35.5( 39.75, 44.5, 47.75, 51.25)“ 90( 101, 113, 121, 130) cm
Finished length: 23.75( 24.5, 26, 27.25, 28)” 60( 62, 66, 69, 71) cm
Sleeve length: 18( 18, 18.5, 19, 19)“ 46( 46, 47, 48, 48) cm

Sleeveless Top
Bust circumference: 34.25( 39, 43.25, 47, 50)“ 87( 99, 110, 119, 127) cm
Finished length: 22.75( 23.75, 25.25, 26.5, 27.25)” 58( 60, 64, 67, 69) cm

Yarn used:
King Cole Opium
Cardigan
MC 278 Leaf - 3( 3, 3, 4, 4) balls
CC 235 Navy - 1 ball for all sizes

Top
MC 278 Leaf - 2 balls for all sizes
CC 235 Navy - 1 ball for all sizes