how to sum two column of subdata sold_that_area and Areatotal on the basis prod_nm

Question

error=arguments must have same length.

this is the data frame from this i made a subdata and on that subdata i want to apply a lapply() to sum the data of same product

 biz1=data.table(
    year=query2$YEAR,
    ProdNm=query2$PROD_NM,
    AreaTotal = as.numeric(as.character(query2$AREATOTAL)),
    Sold_that_area = query2$AREAQTY,
    Month = query2$MONTHNAME,
    Weekand= query2$AREAWEEK,
    AreaName=query2$AREA_NAME,
    Manufacturer=query2$MFG,
    stringsAsFactors = FALSE
  )


here 
subdata4 = reactive(biz1[which(biz1$year == input$YEAR),])
  subdata5 = reactive(subdata4()[which(subdata4()$Weekand == input$WEEK),])
subdata7 = reactive(subdata6()[which(subdata6()$Manufacturer == input$manufacturer),])
this data is coming from

product name      AreaQTY    AreaTotal   
       AA        1        1                
       AA        1        1                
       AA        2       10              
       AA        2       10               
       AA        3      100             
       AA        3      100             

       BB        7       -1               
       BB        7       -1              
       BB        8      -10       


and i want sum of AreaQty And Area total


renderDataTable({
    if(is.null(input$manufacturer) ){return()
    }
    else
    {

i want to sum Sold_that_area and AreaTotal on the basis of prodnm

by(subdata7()[,c("ProdNm","Sold_that_area","AreaTotal")],subdata7()$ProdNm, FUN=colSums)


    }
  },rownames = FALSE, colnames=c("Product Name","Quantity Sold","Total")