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hd 250 Exercise R1 := ρPC1(PC)

R2 := ρPC2(PC)

80

R3 := R1 = AND = AND < R2 160

R4 := π,(R3)

1004 1012Exercise R1 := πmodel(σspeed πmodel(σspeed ≥ (Laptop))

R2 := πmaker,model(R1 Product) R3 := ρR3(maker2,model2)(R2) R4 := R2

(maker = maker2 AND model <> model2)

R3

R5 := πmaker(R4)

maker B Exercise

E R1 := πmodel,speed(PC)

R2 := πmodel,speed(Laptop)

R3 := R1 R2

(PC))

≥

R4 := ρR4(model2,speed2)(R3)

R5 := πmodel,speed (R3 (speed < speed2 ) R4) R6 := R3 – R5

R7 := πmaker(R6 Product) maker B

Exercise R1 := πmaker,speed(Product PC)

R2 := ρR2(maker2,speed2)(R1) R3 := ρR3(maker3,speed3)(R1)

R4 := R1 (maker = maker2 AND speed <> speed2) R2

R5 := R4 (maker3 = maker AND speed3 <> speed2 AND speed3 <> speed) R3 R6 := πmaker(R5)

maker A D

E

R3 := ρR3(maker3,model3)(R1) R4 := ρR4(maker4,model4)(R1)

Exercise R1 := πmaker,model(Product PC)

R2 := ρR2(maker2,model2)(R1)

R5 := R1 (maker = maker2 AND model <> model2) R2

R6 := R3 (maker3 = maker AND model3 <> model2 AND model3 <> model) R5

R7 := R4 (maker4 = maker AND (model4=model OR model4=model2 OR model4=model3)) R6 R8 := πmaker(R7)

maker A B D Exercise

E πmakerσhd ≥ 100 ProductLaptopπmodelσspeed≥3.00PC

πmodel,price πmodel,price σmaker=B σmaker=B PrinterProductLaptopProduct πmodel σcolor = true AND type = laser Printer

πhd (PC1.hd = PC2.hd AND PC1.model <> PC2.model) ρPC2ρPC1PCPCπmodel,price σmaker=B PCProduct–πmakerπmakerσtype=PCσtype=laptopProductProduct

πPC1.model,PC2.model(PC1.speed = PC2.speed AND PC1.ram = PC2.ram AND PC1.model < PC2.model)ρPC2ρPC1PCPC

πmaker(maker = maker2 AND model <> model2)ρR3(maker2,model2)πmaker,modelProductπmodelπmodelσspeed ≥ 2.80σspeed ≥ 2.80PCLaptop