Cast on 90 sts. Rib K1 P1 5cm with 3mm needles.
Change to 3.75mm needles, 20rows stocking st.
Then..
K4, K2 tog, rep from to end.

row 2 and alternate rows purl.

row 3 K9, K2 tog, rep from * to end

row 5 * K8, K2 tog, rep from* to end.

continue to decrease 7 sts across alternate rows until 11 sts remain.
Make bobble and sew seams.