Lisa's mother gave her 3/5*$1200 = $<<3/5*1200=720>>720 for her birthday gift.
She also received 2*$720 = $<<2*720=1440>>1440 from her brother for the gift.
If she still had to find $400 to fully reach her birthday gift cost, it means her gift's total cost was $1200+$1440+$720+$400 = $<<1200+1440+720+400=3760>>3760
#### 3760