[单选题]
A 4.0-N force acts for 3.0 s on an obje:h+ bv +bkrez (/vb ;u)pc:fprct. The force 7cm4avm 7m8 wxsuddenly increases to 15 N and acts for one more second. What impux m7caw7v8m 4mlse was imparted by these forces to the object?
A. $12 \; N \cdot s$
B. $15 \; N \cdot s$
C. $19 \; N \cdot s$
D. $27 \; N \cdot s$