It is the last day of June today. It is Grandma's birthday. Father, mother and I go to see her.

    She lives(居住) with my uncle in a village(村子). Early in the morning we buy a birthday cake and some fruit and go to her home by bus.

    Grandma and uncle are very happy to see us. We give presents(礼物)to Grandma and say “Happy birthday to you!” She is very happy. Then we sit down to talk. Uncle goes to prepare(准备)lunch. The meal( 餐) is very nice. We all like it very much. At 4 o'clock, we say goodbye and go back home.

若$\overrightarrow{a}$，$\overrightarrow{b}$，$\overrightarrow{c}$均为平面单位向量，且$\overrightarrow{a}$+$\overrightarrow{b}$﹣$\overrightarrow{c}$=（$\frac{3\sqrt{3}}{2}$，$\frac{3}{2}$），则$\overrightarrow{c}$=____ 

地面坡度越大，土壤含水率越高，流域汇水速度越快。